Ruby Rods and Musings for the New Year

[SpinozaQ]

Hi! I've reading the forum for a while now, learning all your tips, tricks, secrets. ha. I'm really interested in expanding my electronics hobbiest knowledge and getting into some lasers. I am interested in building a classic Ruby laser. ( Or at least mess around with the crystal right?) I found several laser rods that popped up on ebay. The auctions just ended, they went for 310, 306, and 521 for the larger diameter one.

Ruby Crystal Laser Rod High Power | eBay
Ruby Crystal Laser Rod High Power | eBay
5 8 inch Diameter Ruby Laser Rod High Power | eBay

Is that about what these items are priced at? The ends appeared optically polished, but no way to know for sure I guess.

 

[baddspella]

Oh wow, so your actualy going to beuild a laser diode from scratch ?
If you want to get into lasers maybe just buy a simple DIY with a diode, houseing and driver

But if you do build your own Diode, please show lots of pics!

 

[jeffreythe00]

Not a laser diode. He wants to build a high energy ruby laser. Do some reading on ruby lasers

 

[pschlosser]

so, like...
where's the musings?

 

[Bob_Boyce]

Hi! I've reading the forum for a while now, learning all your tips, tricks, secrets. ha. I'm really interested in expanding my electronics hobbiest knowledge and getting into some lasers. I am interested in building a classic Ruby laser. ( Or at least mess around with the crystal right?) I found several laser rods that popped up on ebay. The auctions just ended, they went for 310, 306, and 521 for the larger diameter one.

Ruby Crystal Laser Rod High Power | eBay
Ruby Crystal Laser Rod High Power | eBay
5 8 inch Diameter Ruby Laser Rod High Power | eBay

Is that about what these items are priced at? The ends appeared optically polished, but no way to know for sure I guess.

Brings back some fond memories. It's been decades since I built one of those.

I suggest you shop around. There are surplus vendors with online stores that sometimes have ruby laser components at fair prices.

You might want to look into some more modern surplus options as well. I picked up a NOS (New Old Stock) flash lamp pumped 6.2 KW pulsed IR laser for $50 a couple of years ago. Water cooled, but I picked up a stainless steel heat exchanger assembly surplus for $25 a few weeks later. The crystal rod from one of those could be swapped out for ruby with a little work. Gas lasers can be fun as well.

Bob

Edit: Here's a link for one surplus site, they have a lot of goodies. Check out the optics pages for example.

American Science & Surplus : Items Just Off the Truck

 

[SpinozaQ]

Ahh. The musings.

Beyond the goal of getting a Ruby laser operational are some experiments. I've noticed in the last year that very small, quite high power 405nm and 550nm LEDs ( not laser diodes ) have become available. These LEDs are capable of 60 lm/watt for the blue, and 120 lm/watt for the green. They can run at 3 watts 100% duty cycle with a bit of cooling. The main package itself is 3mm by 3mm.

Now, imagine a cylinder surrounding a ruby laser rod, perhaps 100mm long, with a diameter of 50mm. That provides an internal area of about 15000 sq/mm. Since each LED only takes up about 10sq/mm 1500 of them will fit on the internal area of that cylinder.

So... With default cooling and running in specifications that's 4.5 KWatts electric. I'm guessing with efficiency losses that a bit less then 2 KWatts of actual light..... but .... that means that 2 Joules per millisecond is available for absorption by the rod, and all at the correct frequency. With the 3 millisecond fluorescence that means 6 Joules are available for stimulated emission.

Thoughts? Show stoppers?

I plan on experimenting with small sets of LEDs first obviously. I believe they could be over driven significantly. Perhaps up to 5 watts electric for the needed 5 millisecond pulse. Of course with LEDs the light output increase has diminishing returns when over-driving.

 

[Teslanium]

The ruby laser is typically pulsed, not CW, I'd like to know how you are going to pulse that cylindrical diode array. And yes, cooling is going to be a primary concern, not just for the laser rod, but for the diodes too.

I think that you have an original and promising idea though! Looking forward to future posts!

Edit: Depending on how much penetration you get of pump light into the rod, you may only need a row on each side (to start)?

Brings to my mind some coiled flash lamps I bought on the 'bay a few years ago. Hmmm...

And REMEMBER this warning from your ebay links:
"Such a laser will be hazardous to operate and should only be done by qualified personnel." Definitely get goggles.

T.

 

[SpinozaQ]

Yes I was planning to operate the system as a pulse. I mentioned a 5 millisecond pulse at the end of my post. Pulsing a diode array is fairly easy, depending on how you construct it. LEDs have rise times in the nano-second range, so millisecond pulses are no problem. ( Often times running at lower duty cycles on LEDs can result in great efficiencies for the same average power. )

Construction of the array would be done in lengthwise pieces, probably resulting in 3 large arrays that would each cover 120 degrees of the rod.

A lengthwise row or two would certainly make a ruby rod florece nicely... ( I would post pics! ) but there is no way it would achieve a population inversion. There is "barely" enough output to get a small rod to lase with 1500 of them. It's really all or nothing for the laser part.

The power supplies on my bench are far more dangerous to my general health then a bit of laser light, but I appreciate the concern. I will have the correct protective glasses on when I attempt first light.